In many industries, in the oil industry in particular, it is necessary to provide cables which are armored to prevent damage to the cable during installation and use. Armored cables are also used in other environments where the cable is potentially subject to mechanical abuse. In the oil industry, electrical cables for down-hole pumps are particularly subject to mechanical abuse during insertion into and removal from the well. In this application, the pump is positioned in the well and the cable is pulled down the well to provide electrical energy to the pump at the bottom of the oil well. During this operation, the electrical cable is subject to being snagged by any number of objects in the oil well casing and in the machinery used to drop the down-hole pump into position. Frequently, it is necessary to lift the pump for servicing, access, or other treatment of the oil well. During this operation, the electrical cable which provides energy to the pump is pulled out of the well and is subject to being snagged in the other direction as it is pulled out of the casing. A failure in the armor of electrical cables is generally referred to in the art as a "holiday". The object of this invention is to provide an improved anti-holiday armor for cables generally and, specifically, for cables which are subject to being snagged in both directions, such as is the case in the oil well applications just described.
Armored cables are, of course, very well known. The following United States and foreign patents, the disclosure of which is incorporated herein by reference, teach various approachments and embodiments of armored cables:
U.S. Pat. No. 242,894 Delany June 14, 1881 PA1 U.S. Pat. No. 294,536 Waring Mar. 4, 1884 PA1 U.S. Pat. No. 327,476 Spalding Sept. 29, 1885 PA1 U.S. Pat. No. 916,741 Lutz Mar. 30, 1909 PA1 U.S. Pat. No. 1,937,054 Cremer et al Nov. 28, 1933 PA1 U.S. Pat. No. 2,453,313 Gordon Nov. 9, 1948 PA1 U.S. Pat. No. 2,531,917 Mollerhoj et al Nov. 28, 1950 PA1 U.S. Pat. No. 3,106,815 Nance et al Oct. 15, 1963 PA1 U.S. Pat. No. 3,334,177 Martin Aug. 1, 1967 PA1 U.S. Pat. No. 3,636,234 Wakefield Jan. 18, 1972 PA1 U.S. Pat. No. 3,742,363 Carle June 26, 1973 PA1 U.S. Pat. No. 3,773,109 Eberline Nov. 20, 1973 PA1 U.S. Pat. No. 3,834,481 Boyd et al Aug. 27, 1974 PA1 Denmark Pat. No. 58,806 June 16, 1941 PA1 Great Britain Pat. No. 22,005 Aug. 16, 1906 PA1 Great Britain Pat. No. 413,295 July 9, 1934
Delany, U.S. Pat. No. 242,894, and Waring, U.S. Pat. No. 294,536 each disclose the use of metal coverings on cables. Spalding, U.S. Pat. No. 327,476, teaches compound electrical cables which include multiple, parallel electrical connectors each enclosed in insulation and in metallic screen and all enclosed in additional metallic screen. Metal wrapped cables of various configurations are disclosed in Lutz, U.S. Pat. No. 916,741, Cremer et al, U.S. Pat. No. 1,937,054, Gordon, U.S. Pat. No. 2,453,313, and Mollerhoj et al, U.S. Pat. No. 2,531,917. Mollerhoj et al discloses a flat electrical cable around which are wrapped two thin metal tapes helically, one above the other. Other armored cables are disclosed in the afore-mentioned United States patents. Danish Pat. No. 58,806, to Standard Electric, discloses an electrical cable construction in which electrically insulated conductors are sequentially wrapped with two copper straps helically overlapping each other wound in one direction and a helically overlapping iron strap wound helically in the other direction, all three of the metal straps being wound from one end of the cable such that the metal straps all overlap the preceding helix in the same manner. The purpose for the metal wrapping in the standard electric Danish patent is not primarily as a mechanical armor and it would, at most, provide holiday protection in only one direction.
United Kingdom Pat. No. 22,005, Henley, discloses an electrical cable which is wrapped with two metallic ribbons from the same end of the cable, the first ribbon being wrapped helically in one direction from the first end of the cable and the second ribbon being wrapped helically in the opposite direction, but from the same end of the cable so that current flowing in the ribbons pass in a helically opposite direction. This arrangement would, inherently, provide some armoring effect but, at the most, would provide holiday protection in only one direction.
None of the prior art provides suitable anti-holiday protection in two directions for submersible cables and cables subjected to two-directional snagging. It is a principal feature of this invention to provide an improved electrical cable which overcomes the deficiencies of the prior art in this and other respects.